The art of printing images with micro-fluid technology is relatively well known. A permanent or semi-permanent ejection head has access to a local or remote supply of fluid. The fluid ejects from an ejection zone to a print media in a pattern of pixels corresponding to images being printed. The fluid is typically dye or pigment based ink. Dye ink is traditionally cheap with a broad gamut of colors. Pigmented ink is generally more expensive, but has longer permanence and higher color stability.
Pigmented ink is also known over time to settle downward in a container leaving rich sediment concentrations near a bottom, while leaner sediment concentrations remain near a top. When printing, ink drawn from a floor of a settled container leads first to excessively densely printed colors and later to excessively lightly printed colors. The variation causes unacceptable visible defects. The former can lead also to clogging of ejection head nozzles if large particles accumulate together in micron-sized channels having fastidious fluid flow standards.
By applying either the Mason/Weaver equation to particle sedimentation, or a numerical analysis using finite element modeling, for instance, the particle concentration of pigment in a container can be fairly predicted over time. In either, locations are revealed in a container where present concentrations match initial concentrations regardless of the length of settling time (also known as the Mason/Weaver invariant point). To accommodate drawing fluid from this point, some manufacturers have raised fluid exit ports to heights measurably higher than floors of containers. While it avoids supplying ink to a printing or imaging device having too dense a concentration, it prevents full use of a container's contents as appreciable amounts of ink rest below the exit port on lowermost surfaces of the container. In turn, some have introduced collapsing container walls to squeeze ink toward the exit port while still maintaining the location of the exit port above the bottom. This unfortunately introduces expense into the manufacturing process and complicates design as pressure regulating devices are sometimes needed.
In other solutions, containers are known with mechanical stir bars or agitating members that roil ink and mix sediments before and during use. While nominally effective, the approach causes expensive/complex manufacturing and necessitates motive force to set agitating bodies into motion. Still other designs contemplate the use of Galileo balls, heaters, agitation by external forces (such as movement of a tank carrier), ink recycling, vibration, posts, segmented tanks, shelves, stand pipes, or multiple fluid ports, to name a few. Most are ineffective or impractical. None provide economic advantage or acceptable relief across all facets of design, manufacturing and use.
Accordingly, a need exists in the art to deliver imaging devices an entirety of pigmented ink in a container. The need extends not only to an economical solution but to delivering ink in a manner that its concentration has uniform properties over the life of the container, independent of usage rate, temperature or other imaging device conditions. Additional benefits and alternatives are also sought when devising solutions.